Bipolar disorder (BD) is a devastating mental illness - twice as expensive as major depression in terms of health care costs and lost productivity - with a very poor prognosis for patients. Unfortunately, BD is on the rise in children and adolescents, with a 40% increase in diagnoses in recent years, and nearly half of BD- adults report that their illness started in childhood. Despite this, few studies have used neuroimaging methods, such as functional magnetic resonance imaging (fMRI), to directly compare brain\behavioral alterations in BD- youths to those in BD-adults. Further knowledge of these neural alterations could make interventions earlier, more targeted, and more effective. This career development project will train Ezra Wegbreit, PhD, in several key areas to help him develop professionally and to complete a research project directly comparing brain\behavioral alterations in BD-youths to BD-adults. Dr. Wegbreit will learn about the assessment of clinical symptoms in youths and their use in diagnosis with his primary mentor, Daniel P. Dickstein, MD. Dr. Dickstein will also mentor Dr. Wegbreit in resting-state fMRI data analysis techniques. Gabrielle Carlson, MD, of the Stony Brook School of Medicine will serve as an external consultant and provide Dr. Wegbreit with a different perspective on diagnosis and assessment of psychopathology, especially in pediatric bipolar disorder. Dr. Wegbreit will learn about the assessment of clinical symptoms in adults and their use in diagnosis from his co- mentor, Mark Zimmerman, MD. To gain a better understanding of the meaning behind neural differences between youths and adults with BD, Dr. Wegbreit will learn about computational modeling of cognitive processes and their relation to fMRI measures from co-mentor Michael J. Frank, PhD. In addition, Dr. Wegbreit will learn how to analyze diffusion-weighted MRI data from co-mentor David H. Laidlaw, PhD, in order to investigate white matter structural changes in youths and adults with BD. The research project will compare BD-youths and BD-adults as they complete a) an event-related fMRI emotional face Stroop task probing the neural mechanisms underlying the interaction between emotion recognition and cognitive control systems, b) behavioral tasks measuring emotion recognition and cognitive control, c) resting-state fMRI measuring task- independent functional connectivity, d) diffusion-weighed magnetic resonance imaging measuring white matter connectivity, e) self-report dimensional measures of psychopathology, and f) clinician-rated diagnostic and dimensional assessments. Matched youth and adult healthy control participants will be recruited to serve as a developmental comparison group. The goal of this project is to advance our models of the developmental trajectory of BD, potentially leading to improved assessment, diagnosis, and treatment of youths and adults with BD. These research and training activities will help Dr. Wegbreit become an independent investigator conducting developmentally informed patient-oriented research in bipolar disorder and other mood disorders.